3rd RCCB Fault??

[1valiant]

Am I missing something here or is it just plain bad luck? I've recently tested a fuseboard and the RCD failed (MEM A100HE 100AMP 30Ma RCD). Sent off for a new one and it failed got another failed again.
Checked multi-tester on another board, tester works fine. It's on a TN-S system, there's a 16mm earth clamped onto the incoming leading straight to the fusebord, the earth clamp is tight. all bonding is good. Am i missing something or have I just come across a batch of dodgy RCCB's.

Cheers.
Darren.

 

[rocker]

Are you sure it's not an s type or a 100mA?

 

[NoSparks]

What tests are you doing on them? Remember an insulation test will blow them.

PS you say RCCB at one poiint and RCD at another - which do you mean?

Edit. Sorry I normally associate RCCB with incommers, but technically this is not so.

 

[topquark]

Yep, could be an A100ME (then it'd be 100ma).

 

[rocker]

RCCB is the correct term for RCD as far as I know. They are the same thing.

 

[1valiant]

Just to clarify it's a MEM A100HE 100AMP 30ma RCCB.

Cheers
Darren.

 

[topquark]

OK, I rather assumed it's failing it's RCD testing. What test(s) are you saying it has failed?

 

[1valiant]

Just RCD x.5, x1 and x5. (No IR test)

 

[topquark]

To be sure we're understanding this, it's failing all 3 (possibly 5) of those tests???

So it trips at 0.5X ? (coz that's the only way it would fail ... it shouldn't trip at all).
and
It doesn't trip, in time, at 1X 30ma (0 or 180 degrees)
and
doesn't trip, in time, at 5X 30ma (0 or 180 degrees) ?

In the latter 2 (4) cases is it not tripping at all or taking longer than 411.3.2.2 dictates (0.4S for your TNC-S 230V system).

I'd be double checking my wiring in the CU first. Ensure you have reconnected the main earth after testing Ze and ensure that you have no temporary links anywhere.

What is the Ze you have and where are you performing the tests for this (32A RFC at the socket for example?)?

 

[Des 56]

I am going to take a guess that you are not testing at source, and applied loads are screwing up the testing
Either that or you are extra unlucky


If I'm wrong I am sorry

 

[Dunc]

This might be of interest.

LINK

If the RCCB operates when you press the test button but not when applying a 30mA test using your meter then you may be experiencing the same problem i had yesterday.

 

[topquark]

This might be of interest.

LINK

If the RCCB operates when you press the test button but not when applying a 30mA test using your meter then you may be experiencing the same problem i had yesterday.

Very usefull, thanks Dunc!

 

[Dunc]

Just Googled the RCCB in question, guessing it's from a Memera 2000 CU which is the same CU i had the issues with the RCBO on. The RCD in that board tripped very slowly (180ms on x1) which seemed odd but still a pass. This was with my croc clips clamped to the neutral bar and the busbar at the base of the RCCB. Thinking even more now that you might be having the exact same problem so try plugging your meter in at a remote socket on the ringmain and give it a whirl. Obviously ensure all equipment has been disconnected from the socket circuit you are testing from as some electronic gear will not appreciate losing power 4 times in quick succession.

 

[1valiant]

Yes, it sounds like the same problem it's a Memera 2000CU. and I'm testing from a radial coming out next to the board. No equipment on circuit, Ze 0.05. very frustrating,

Darren

 

[jks]

have yu tried it connected up using a safe block out of circuit to prove rcd or installation fault